JPH0567439B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is used in recording devices such as thermal printers and thermal typewriters, in which heat-melting ink is gradually transferred to a receptor such as recording paper by heating with a thermal head. The present invention relates to a method for producing a multiple-use thermal transfer recording medium that can be used multiple times at the same location. [Prior Art] Conventionally, this type of multi-use thermal transfer recording medium uses a resin that is incompatible with heat-melting ink, and the ink is contained in a sponge layer formed of this resin. with the configuration that is
It is known that a highly cohesive fine powder is mixed with the ink and a barrier layer formed by the agglomeration of the fine powder is provided. [Problems to be Solved by the Invention] However, in the former method, the ink is held so as to be wrapped in the resin that forms the sponge layer, so the initial density of the formed image is low, and the ink is not formed with high density and sharpness. I couldn't get a good impression. Further, in the latter case, since the porosity between the aggregated fine powders was small, the amount of ink retained was small, resulting in low printing density and a small number of printings. In view of these circumstances, the present invention aims to eliminate the above-mentioned drawbacks. [Means for Solving the Problems] In order to achieve this object, the present invention impregnates porous powder particles with a porosity of 50 to 97% with a hot melt ink, and then inks the ink-impregnated porous particles. Fine powder particles are dispersed in a solvent solution of a binder agent that is substantially incompatible with the heat-melting ink, and then applied onto a base material and dried to form a porous layer impregnated with the ink on the base material. The ink-containing layer is formed by combining powder particles with each other using the binder agent. [Function] With this configuration, the heat-melting ink is melted by the heating of the thermal head, gradually oozes out from the porous powder, and is transferred to a receptor such as recording paper to form an image. It happens. [Effects] As a result, compared to the conventional sponge layer, the ink is not trapped in the resin, and the heat-melting ink is transferred to the receptor with low thermal energy, which is advantageous. Compared to the conventional method using agglomerated fine powder, the ink retention rate is higher,
Printing with high density can be achieved continuously. As a result, compared to conventional products, the initial print density is high and the print image at that high density lasts, making it possible to use the printhead many times. [Embodiments] Next, the present invention will be specifically explained. The porous powder has an average particle diameter of 1 to
A material with a diameter of 20 μm and a porosity of 50 to 97%, particularly 60 to 93% is suitable. Here, the porosity is the average value of the ratio of the volume of voids to the total volume of powder particles. When the average particle diameter is smaller than 1 μm, most of the surface of the powder is covered with the binder agent, and the ink does not bleed out. Also, the average particle size
If it is larger than 20 μm, part of the printed image will be chipped and the printing quality will deteriorate. If the porosity is less than 50%,
Not only does the number of uses decrease significantly, but the print density also decreases rapidly with use. In addition, the porosity
When it is greater than 97%, the rigidity of the powder decreases and there is a risk that it will break when mixed with the binder agent. Examples of this porous powder include inorganic porous powders such as diatomaceous earth, zeolite, and bentonite, and organic porous powders such as urethane pore powder. The binder agent is one that is incompatible or poorly compatible with the heat-melting ink, has adhesive properties to the base material of the recording medium and porous powder, and does not melt when heated by the thermal head. Common examples include heat-melting resins or thermosetting resins having a softening point of 70° C. or higher, such as polyester resins, epoxy resins, styrene resins, polycarbonate resins, cellulose acetate butyrate, ethyl cellulose, and polyamideimide resins. These resins may be used alone or in combination of two or more. In addition, one or more kinds of suitable additives may be added in appropriate amounts depending on the purpose. It is appropriate that these binder agents be blended in an amount of about 1 to 15 parts by weight per 10 parts by weight of the porous powder. As the heat-melting ink, those having the same composition as those conventionally used as solid inks for thermal transfer recording media can be used, but in particular those having a viscosity of 10°C at a temperature 30°C higher than the melting temperature can be used.
~500cP (measured value using a B-type viscometer),
It is suitable that the melting temperature is 50 to 120°C, and preferably adjusted to be lower than the softening point of the binder agent. Coloring agents for hot-melt ink include not only black pigments such as carbon black, but also blue, red,
A coloring agent such as yellow may be used to form a colored image. As these coloring agents, any of those used in conventional one-time thermal transfer recording media can be used. Appropriately, this heat-melting ink is blended in an amount of about 3 to 20 parts by weight based on 5 parts by weight of the porous powder. The following method can be used to impregnate porous powder with liquid ink obtained by heating and melting hot-melt ink. One method is to impregnate the ink into the powder by placing the molten ink and porous powder in a mixer such as a despar and mixing them, and the other method is to mix the molten ink and porous powder in a mixer such as a desper. This is a method of vacuum impregnation using a vacuum impregnation device after mixing with the body. The porous powder impregnated with the hot-melt ink by these methods is heated in a state in which the ink is hot-melted, and then the binder agent solution (the solvent used is almost the same as the hot-melt ink and the porous powder). (preferably one that does not dissolve) is applied to a substrate and dried to form an ink-containing layer. The thickness of the ink layer after drying is suitably 1 to 20 μm. Examples of the base material include plastic films such as polyester, polycarbonate, nylon, and polypropylene, high-density papers such as moisture-proof cellophane, condenser paper, and glassine paper, or thin sheets with metal vapor-deposited or laminated on one or both sides thereof. used. [Example] Next, the present invention will be described with reference to Examples. Examples 1 to 4 and Comparative Examples 1 to 2 The porous powders shown in Table 1 were impregnated with the hot melt inks shown in Table 2. Impregnation with ink was carried out by mixing hot molten ink and porous powder and vacuum impregnation using a vacuum impregnation device. The porous powder impregnated with the ink in this manner is mixed with the binder solution shown in Table 1 in a state in which the ink is thermally melted, and the resulting mixture is applied to the substrate shown in Table 1. An ink-containing layer having the thickness shown in Table 1 was formed by coating and drying to remove the solvent.

【table】

【table】

[Table] Note 1: Oil dye manufactured by Orient Chemical Co., Ltd. The multi-use thermal transfer recording media obtained in Examples 1 to 4 above were used in a thermal printer (WP-55) manufactured by Canon Inc. to perform recording. Printing was performed 10 times on white recording paper using the same location on the medium, and the OD value of each print was measured using a Macbeth densitometer. The results are shown in Table 3. For comparison, a sponge layer type multi-use thermal transfer recording medium (Comparative Example 1) shown in Example 1 of JP-A-54-68253 and JP-A-57-
Using the fine powder agglomeration type multi-use thermal transfer recording medium (Comparative Example 2) shown in Example 1 of Publication No. 160691, impressions were formed in the same manner as above, and the OD value of each impression was determined using a Macbeth densitometer. was measured. The results are shown in Table 3.

【table】

[Table] When forming an image using a conventional one-time thermal transfer ink ribbon, the initial
The OD value was 1.1-1.3.

Claims (1)

[Scope of Claims] 1. Porous powder particles having a porosity of 50 to 97% are impregnated with a heat-melting ink, and then the ink-impregnated porous powder particles are substantially non-stick to the heat-melting ink. A compatible binder agent dispersed in a solvent solution is applied onto a base material and dried, and the ink-impregnated porous powder particles are bonded to each other by the binder agent on the base material. A method for producing a multi-use thermal transfer recording medium characterized by forming a layer. 2. Claim 1, wherein the porous powder particles are vacuum impregnated with the melted hot-melt ink.
Manufacturing method described in section.